ON THE NATURE OF FERMENTATION 337 
ferment is capable of self-multiplication. That I believe to be the essential 
property of a true fermentation. Now, in this particular case, I have already 
said it is admitted on all hands that the yeast plant is the cause of fermentation. 
Persons may differ as to how the development of the yeast plant gives rise to 
the resolution of the sugar into the alcohol and carbonic-acid gas ; but all now 
agree that, somehow or other, the organism causes the fermentation. Now, 
is it the case that all true fermentations are caused by the development of organ- 
isms? That, gentlemen, is the question which it is desirable that we should be 
able to answer. 
Take, for example, the case of the putrefactive fermentation of blood. We 
all know that, if blood be shed from the body into any vessel without special 
precautions, in a few days it putrefies. The bland nutrient liquid, soon after 
leaving its natural receptacle, becomes foul, acrid, and poisonous; a change 
fully as striking as that which grape-juice undergoes in the alcoholic fermenta- 
tion. Here, on the other hand, we have a vessel (a liqueur-glass) into which 
blood was received with special precautions. In the first place, the glass, covered, 
as you see, with a glass cap and a glass shade, with a view of preventing the 
access of dust, and standing upon a piece of plate-glass, had been heated to about 
the temperature of 300° Fahr., and cooled with an arrangement which ensured 
that the air which entered during cooling was filtered of its dust ; so that we 
were perfectly sure that the glass contained at the outset no living organisms. 
Then, in the second place, the glass had been charged from a flask like this, 
provided with a spout. It contains, as you see, a glass tube introduced into it ; 
it is stuffed well with cotton-wool between the neck of the flask and the tube, 
there 1s a piece of cotton-wool over the end of the tube, and another piece is 
tied securely over the spout of the flask. The flask so arranged was heated 
just as the glass had been heated. It is not necessary to have the temperature 
so high as to singe the cotton. Heat far short of this is adequate, according 
to my experience, to make perfectly sure that you destroy all living organisms. 
The flask having been thus prepared, the jugular vein of an ox was exposed and 
divided, with precautions against the entrance of anything putrefactive,' and, 
the cotton cap having been taken off from the end of the tube, the vein was 
slipped over the tube and securely tied on, and then the hand of the assistant, 
who previously restrained the flow of blood, being relaxed, blood was permitted 
to flow into the flask. Then, before coagulation had time to take place, this 
and various other similar glasses were charged after the removal of the cotton 
cap from the end of the spout. Now, the first thing that may strike you is the 
' This was secured by washing the skin and the instruments with a strong solution of carbolic acid 
(1 to 20), and performing the operation under a carbolic spray. 
LISTER I Z 
